Explanation:Compare these two close-up
pictures taken on sol 20 (left) and sol 24 of
a trench dug in the Martian surface by NASA's
Phoenix Lander.
Those sols of the Phoenix Mission
(a sol is a Martian day),
correspond to June 15 and 18 on planet Earth.
Light-colored, dice-sized chunks, visible in the lower left shadow region
of the trench in the sol 20 image
have vanished by sol 24 --
a strong indication that the chunks were ice uncovered
by digging the shallow trench.
The vanishing act likely demonstrates the
sublimation of ice in the
trench, a process similar to evaporation, in which the ice went directly
from solid to gas after it was
exposed to sunlight and the thin, dry
Martian atmosphere.